It is known that one can use for the low-pressure polymerization of olefins catalytic systems containing a halogenated derivative of a transition metal and an organometallic compound. It is also known that the derivative of the transition metal can be fixed onto an oxide support such as an alumina, an aluminosilicate, a silica or a titanium oxide. Such catalysts and methods of making them have been described in British Pat. No. 823,024, U.S. Pat. Nos. 3,166,542, 3,216,982 and 3,506,633 and French Pat. Nos. 1,349,864 and 1,473,568. According to these processes the fixing of the derivative of a transition metal is carried out by chemical reaction from a solution in a hydrocarbon or from vapors of the derivative of the transition metal. The conditions of operation are selected so as to bring about the complete evacuation of the hydrogen halide which is formed during the course of the fixation reaction. The catalytic systems obtained by this mode of operation have a very low productivity, of the order of a few tens of grams of polymer per gram of catalyst.
A copending application by applicants herein, U.S. Ser. No. 153,788, filed June 16, 1971, sets forth an improved process for catalyzing olefins with certain activated alumina cocatalysts which results in greatly increased productivity. However, even greater productivity is desired, and in addition it is desired that the polymers formed have a lower melt index.